An Orbiting Atmospheric Gatherer

[paul_klinkman]

"This 'scenerio' is for an instantenous rendezvous."<br /><br />An instantaneous rendezvous is when two objects meet at, relative to each other, hundreds of kilometers per hour. I had in mind a much more gradual rendezvous, steadily slowing to perhaps 1 kilometer per hour at the docking point. <br /><br />I have played moon landing simulator programs on computers where the goal is to land slowly and safely on the moon, and not to plow into the moon. The process is not easy for a human pilot - a reasonable computer program could perform the landing maneuver better than a human pilot. At least once in the game I came close to landing, hit the fuel too hard and bounced away, then came back a second time for a landing. My landing wasn't exactly instantaneous, but it was within the game's propellant parameters.<br /><br />A rendezvous scenario in microgravity should be a bit simpler than landing on the moon because of the lack of gravity, and the active rendezvous craft can miss the target and turn around instead of crashing. <br /><br />We need to find out why you think the rendezvous needs to be instantaneous. What's going to happen to two craft in microgravity, travelling pretty much in parallel, five seconds after the chasing craft misses its docking ring at 1 kph? Why can't we recover for another try ten seconds after a miss? Why don't we have minutes of docking time to work with? What is this instantaneous business?<br /><br />"It can't happen, real work effects com into play. LV trajectory variations due to actual launch time, winds, actual performance from engines, guidance errors, and other influences will prevent the LV from arriving at the proper position."<br /><br />Why can't a computer program compensate on the fly for winds and actual performance from engines? We can track rockets. Perhaps nothing can correct a terrible guidance error due to a computer programming goof, but that error won't be repeated a second time. The offending computer programmer will

 

[jimfromnsf]

"1. An instantaneous rendezvous is when two objects meet at, relative to each other, hundreds of kilometers per hour. I had in mind a much more gradual rendezvous, steadily slowing to perhaps 1 kilometer per hour at the docking point. <br /><br />2. A rendezvous scenario in microgravity should be a bit simpler than landing on the moon because of the lack of gravity, and the active rendezvous craft can miss the target and turn around instead of crashing. <br /><br />3. We need to find out why you think the rendezvous needs to be instantaneous. What's going to happen to two craft in microgravity, travelling pretty much in parallel, five seconds after the chasing craft misses its docking ring at 1 kph? Why can't we recover for another try ten seconds after a miss? Why don't we have minutes of docking time to work with? What is this instantaneous business? <br /><br />4. Why can't a computer program compensate on the fly for winds and actual performance from engines? We can track rockets. Perhaps nothing can correct a terrible guidance error due to a computer programming goof, but that error won't be repeated a second time. The offending computer programmer will be transferred to the IRS."<br /><br /><br />1. Which means both vehicles are in the exact same orbit. The time to achieve this<br /><br />2. Actually, it is the opposite. Landing doesn't involve a moving target and relative motions. Rendezvous is harder than a video game. There is no 'turning around" for a missed approach. It would take more time and fuel to readjust the orbits to enable another approach. <br /><br />3. Instantaneous is because you want one to do this for a suborbital trajectory. Rendezvous IS the point of getting two spacecraft traveling "in parallel" The issue is that is takes some time to achieve this, the minimum is around 3/4 orbit as Gemini 11 did (and the launch vehicle is the chaser). If there is a miss, it is going to take a lot more than 10 seconds to recover and re establis

 

[paul_klinkman]

"Do you really understand orbital mechanics or launch vehicle trajectories?"<br /><br />I'm not great but I'm not too bad. I've written at least one earth-moon-payload orbital simulation system for my own studies. BTW, you showed your detailed knowledge of launches with this last post. Earlier on I was scared off by the very idea of an instantaneous rendezvous. It sounds like some kind of crash.<br /><br />"The issue is that is takes some time to achieve this, the minimum is around 3/4 orbit as Gemini 11 did--"<br /><br />I'm concerned that the computer chip technology in Gemini spacecraft consisted of 8 or 16 transistor junctions on a single computer chip. I may not be as familiar as you with the hardships that the space program overcame (and this knowledge is useful), but I have an intuitive sense that guidance systems can do better now than we could with mid-60s computer technology. If we can't perform a rendezvous because the technology is so hard for us, maybe the Chinese military can do it for us. They staged a pinpoint high velocity rendezvous with one of their old satellites earlier this year.

 

[kelvinzero]

Well I certainly don't! <img src="/images/icons/wink.gif" /><br /><br />Who are the orbital mechanics gurus on this site? It's getting so's we need arbitration!<br /><br />But I still think it deserves its own thread. For starters it is just as relevant to cheap oxygen launched from the moon.<br /><br />Hey Paul,<br />Do you really need to launch something to prove this idea? I sort of assumed someone would have test faculties for bombarding materials with simulated atmosphere. Does your scheme rely on freefall?<br /><br />Also, Ive googled the mercury pumps. I still dont really understand them except that they seem to use mercury droplets to do the same job as turbine blades. The one I think I understood used gravity to collect the mercury. How do you stop mercury particles from wondering off?

 

[gunsandrockets]

<Sorry, I've been getting a bunch of flak. ><br /><br />So I've noticed. No worries, no offense taken. Just don't let the flakster get under your skin.<br /><br /><If we can perform propellant gathering at a very cheap price, and if we can master these rendezvous maneuvers, then our launch options open up. Scramjets no longer have to reach Mach 25. Single stage rockets don't have to reach orbit. Orbit gets cheap fast. This is what you have dreamed of. I'm sitting on some other outlier applications and this is no outlier, this is the main course. /><br /><br />Okay. But you would have an easier sell by promoting the non-suborbital refuelling applications first. Your concept is a winner even without the sub-orbital ap. <br /><br />I suggest contacting Jon Goff over at Selenian Boondocks he is one of the most vocal champions of orbital refuelling who blogs about the subject. See this link...<br /><br /><br />benefits-of-orbital-propellant-transfer

 

[jimfromnsf]

"I'm concerned that the computer chip technology in Gemini spacecraft consisted of 8 or 16 transistor junctions on a single computer chip. I may not be as familiar as you with the hardships that the space program overcame (and this knowledge is useful), but I have an intuitive sense that guidance systems can do better now than we could with mid-60s computer technology." <br /><br />It has nothing to do with computational power nor the guidance system (and Gemini 11 has ground support). Computers don't change the physics. It takes finite amounts of time. Computers of todays would have have provided the same data as the ones used. The technique now isn't much different than back then, just different approach directions.<br /><br />"If we can't perform a rendezvous because the technology is so hard for us, maybe the Chinese military can do it for us."<br /><br />Now you are playing into my hand. That was an 'instantaneous" rendezvous which is normally called a collision and I believe there was velocity differences on the order of several KM per second. This is what happens when a suborbital vehicle meets and orbital one. <br />The Chinese and the old US ASAT work the same way. It is like using a baseball glove to knock a flyball out of the air. It would look like my same diagram, except the ellipse would be several orders narrower ( and it would go higher)

 

[paul_klinkman]

All I'm saying is that whoever wields power in the U.S. occasionally sets up a "can't do" space program. The Soviet Union beat us into space with Sputnik and with Yuri Gagarin on a little tiny budget. Now the Chinese have launch vehicle steering capabilities that we don't have. I'll admit that there are t&%$#@! technical issues to a dependable rendezvous system, if you'll re-examine your "it'll never work" claim. In space, never is a long time these days, especially if there's money to be made.

 

[jimfromnsf]

"Now the Chinese have launch vehicle steering capabilities that we don't have."<br /><br />I never said that. <br />The booster and the kill vehicle for an ASAT have very different requirements from a launch vehicle and rendezvous spacecraft. <br /><br />The ASAT kill vehicle is very light and it has a high T/W. A spacecraft is much heavier and has a low T/W. <br /><br />Very different solutions are used to "meet" in space. The ASAT, traveling much "slower" than the orbiting vehicle, only has to get in the way and cross the orbit of the target,<br /><br />The US has used former ICBM's and an aircraft launch missile to propell their versions of kill vehicles. BTW, the kill vehicles were from a few hundred pounds to under 100 lbs.<br /><br />"All I'm saying is that whoever wields power in the U.S. occasionally sets up a "can't do" space program. "<br /><br />It has nothing to do with this. There is no more engineering (short of unlimited thrust) left to be done in the rendezvous process. The actual process takes a finite amount of time. Trying to do it faster would be like using a dragster to go to the grocery store, it has too high of acceleration and can't stop very well.

 

[rocketman5000]

In venus orbit you could capture the sulfuric acid from the clouds and the CO2 from the atmosphere and use it to break down the CO2 to methane and O2.

 

[paul_klinkman]

Caution: Venus has no geomagnetic field, and the gatherer was made for an electromagnetic tether. It's possible to restore the gatherer's momentum by other means, but it could be expensive.

 

[j05h]

<i>> Who are the orbital mechanics gurus on this site? It's getting so's we need arbitration! </i><br /><br />Jim is as close to an OM guru as we have, and Shuttle_guy and Erioladastra, they all work with actual spacecraft. We could really use a regular poster who was solidly skilled in OM, but any of the degreed Aero guys/rocket engineers here know enough about it to give accurate advice. AFAIK, what Jim is saying is exactly correct. I thought we went through this earlier in this thread? If there is someone here who really knows orbital mechanics, please speak up.<br /><br /><i>> JimfromNSF: "This is why the shuttle takes it's time, so it doesn't miss. "</i><br /><br />I think what Paul_Klinkman is confusing is rendezvous and docking maneuvers, mostly because of the differences in velocity. Rendezvous is a process of accelerating several thousand kph, performing a circularization burn and orbit phasing to match another spacecraft's orbit. Docking is the process of covering the "last mile" using a craft's RCS, leading to a relatively soft contact. The other concept dockings he proposes have hundreds to thousands of kph in velocity differences. I think he is suggesting an arc of flight that goes from the ground to station docking in one motion. He is implying a "Landing burn" like an aircraft as it approaches the station, or that the station deorbit itself to meet the craft (which doesn't work). Actual spaceflight orbits are much more involved.<br /><br />I recommend "Rocket Propulsion Elements An Introduction to the engineering of rockets" by George P. Sutton for Paul_Klinkman and anyone interested in rockets. For P_K, check out the sections on flight performance (esp. Sections 5, Spaceflight and 6, Rotational and Space Trajectory Correction Maneuvers) and nozzle design. It's a very dense textbook, is extremely complex and incredibly informative. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[paul_klinkman]

"I think he is suggesting an arc of flight that goes from the ground to station docking in one motion."<br /><br />Yes. I suppose that "one motion" requires precision real-time tracking of the launched craft's position, through GPS and/or through visual tracking from the orbiting or semi-orbiting craft. Tracking information must be passed onto the launched craft while the launch rocket's second stage is still engaged. The rocket's thrust must decrease or shut off at a precise time just like a lunar lander's thrust does. I also assume that a computer program can dock as well as a human pilot and with far less time wasted.<br /><br />I can recognize one "last mile" problem with docking: burning a retrorocket directly at the target vehicle is going to affect the target vehicle. Two solutions to the problem are: point retrorockets 30 degrees off to the side and approach the target in a spiral, or have the target vehicle compensate for any such propellant backwash against its outer hull.<br /><br />I recognize that "one motion" has never been tried and it might be expensive to develop. However, NASA has coordinated its first stage rocket separations and second stage burn commencements without too much trouble.<br /><br />"He is implying a "Landing burn" like an aircraft as it approaches the station,"<br /><br />You're referring to the way a jet engine slows a plane down on the runway after touching its wheels down? The landing burn of the lunar lander would be more descriptive, as the goal is to drop relative velocity to nearly zero, given a fixed amount of maximum thrust, in a time-pressure environment.<br /><br />"or that the station deorbit itself to meet the craft (which doesn't work)."<br /><br />"The station"? Not the entire gatherer, of course, just a space tug very cheaply fueled by the gatherer craft at a slightly higher orbit. <br /><br />"Deorbit"? It's theoretically possible for a well-powered rocket in orbit to slow down a few hundred kph, drift for two minutes,

 

[j05h]

<i>>Yes. I suppose that "one motion" requires precision ...<br /> "Deorbit"? It's theoretically possible for a well-powered rocket in orbit to slow down a few hundred kph, drift for two minutes, and then accelerate to its original orbit without deorbiting. ...</i><br /><br />The "well powered rocket" part is the kicker. You might get that kind of performance with a NERVA our nuke-powered VASIMR but probably not from chemical rockets. You're original docking description of the station lowering to "pick up" the craft (which would result in deorbit) has perhaps clouded my understanding of what you're describing. <br /><br />I'm not qualified to really comment on implementing the "one motion" concept, but it seems unrealistic with current technology. It is similar to one of the Bolo concepts, which features a rotating tether snatching payloads from hypersonic aircraft. The problem with that is that the payload is suddenly accelerated. It's maybe possible but not currently likely. The biggest problem with the idea is that without orbital phasing there will be significant sideways momentum. (can someone correct me on that?)<br /><br />A lot of your ideas are interesting but need physics and operational checks.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[jimfromnsf]

"1. I think he is suggesting an arc of flight that goes from the ground to station docking in one motion."<br />Yes. I suppose that "one motion" requires precision real-time tracking of the launched craft's position, through GPS and/or through visual tracking from the orbiting or semi-orbiting craft. Tracking information must be passed onto the launched craft while the launch rocket's second stage is still engaged. The rocket's thrust must decrease or shut off at a precise time just like a lunar lander's thrust does. I also assume that a computer program can dock as well as a human pilot and with far less time wasted.<br /><br />2. I can recognize one "last mile" problem with docking: burning a retrorocket directly at the target vehicle is going to affect the target vehicle. Two solutions to the problem are: point retrorockets 30 degrees off to the side and approach the target in a spiral, or have the target vehicle compensate for any such propellant backwash against its outer hull.<br />You're referring to the way a jet engine slows a plane down on the runway after touching its wheels down? The landing burn of the lunar lander would be more descriptive, as the goal is to drop relative velocity to nearly zero, given a fixed amount of maximum thrust, in a time-pressure environment.<br /><br />3. At the very least, the rocket could point its engine downward and gently compensate for the .01 gee force pulling it downward, maintaining its circular orbit at the lower velocity for a long time."<br /><br />1. Most launch vehicles are already in orbit at lower altitudes when their engines shutdown. That is the reason for the spacecraft to use thrusters to adjust the final orbit.<br /><br />LV upperstage stages use high thrust engines (compared to spacecraft) and are not throttled. They are not appropriate for the maneuvers required for rendezvous<br /><br />2. Which vehicle has the retros? The launcher? A retro burn is going to put it in a lower orbit and it is going to speed

 

[kelvinzero]

I like the sound of that book:<br />http://www.amazon.com/Rocket-Propulsion-Elements-George-Sutton/dp/0471326429/<br /><br />I would like to hear more discussion on the actual gatherer concept though. I havent heard any serious arguments that it is not something worth getting excited over. That blog link suggesting inorbit refueling has serious advantages even without a gatherer only increases my interest.<br /><br />Also, surely this idea can be convincingly demonstrated without actually launching it (unless it specifically requres freefall). Wouldnt people already have developed labs for testing materials in simulated LEO environments? I imagine something like a vaccum chamber and an ion gun projecting the appropriate mixture of elements at the appropriate velocities. <br /><br />FOUND SOME LINKS TO ORBITAL ENVIRONMENT SIMULATION: (by googling orbital environment simulator)<br />http://gltrs.grc.nasa.gov/cgi-bin/GLTRS/browse.pl?1993/E-7797.html<br />http://www.grc.nasa.gov/WWW/epbranch/space/sesabs.htm

 

[paul_klinkman]

I'm moving this sub-thread to a new thread: Reaching Orbit with an Assist.

 

[paul_klinkman]

I hope to put on an informal discussion of the Orbital Atmospheric Gatherer at noon, probably on Tuesday, May 22, at the ATWG conference in Dallas.

 

[kelvinzero]

Wrong hemisphere, damn <img src="/images/icons/wink.gif" /><br /><br />Post back here how it goes.

 

[gunsandrockets]

So? How did it go? Did the audience love it or hate it?

 

[jimfromnsf]

What was the outcome?

 

[jimfromnsf]

"Dr. Wilkes is scheduled to present a paper at the AIAA Space 2007 Conference and Exposition on September 18-20 at the Long Beach, CA Convention Center"<br /><br />There was no paper presented.<br /><br />Also what would an associate Professor of Social Science & Policy Studies with a PHD in Sociology know about an Orbiting Atmospheric Gatherer.<br /><br />There is your reason for the lack of orbital mechanics knowledge which make the rest of the topic suspect

 

[kelvinzero]

And yet:<br /><blockquote><font class="small">In reply to:</font><hr /><p>I've been working on it with a project team at Worcester Polytechnic Institute since last September. We presented at the IASTS conference on February 3.<p><hr /></p></p></blockquote><br />And yet he had the enthusiasm to get a group working on an interesting topic that could have given them an interest in continuing their education in the space field, and maybe some of them were very very bright young people that would be a gift to any field they applied themselves to.<br />And all they had to do to change the whole picture was demonstrate a vaccum pump that could handle particles coming in at high speed. Not solve the problems of regaining orbital speed using electronic propulsion. Lots of other bright people are doing that. Not to solve problems of orbital mechanics that experts in the field know are just too hard.<br /><br />And all <i>we</i> had to do was provide a little encouragement to focus on the smaller problem of the vaccum pump, leave the harder problems that are irrelevant or being handled by eg the VASMIR guys, maybe dig up some <i>friendly</i> engineer with space industry experience to put them on track and encourage them in their education.<br /><br />And if they made no progress on the vacuum pump during the project then nevertheless in their next positions each of these people might have found themselves in the company of people with more experience that might have sparked the idea that WOULD lead to a solution.<br /><br />But did you encourage them to work on the vacuum pump? No, you specifically tied the value of the entire idea to the irrelevant orbital assist idea where you could squish it in detail.<br /><br />Do you think it remotely relevant to the gatherer concept whether a bunch from Worcester Polytechnic can change the world? Of course they probably cant. They are about as likely to perfect this device as build the rocket that launches it. (the storage tanks alone are considered an issue

 

[sundoccer]

Agree with you, sure hope the're giving it a go too. As others have already stated such a propulsion system would be perfect for lofting components for a space-based power-beaming satellite into geosynch orbit, like in the book Sunstroke by David Kagan.<br /><br />There is an excellent new article on space.com describing the need and willingness of the U.S. government to build and deploy this type of satellite. <br /><br />http://www.space.com/businesstechnology/071012-pentagon-space-solarpower.html<br /><br />Good luck to the project team at Worcester Polytechnic Institute! If they can pull it off they'll get one of the biggest contracts ever.

 

[gunsandrockets]

I see you are now posting again at SDC after a long absence. Jimfromnsf has been banned so that distraction is now gone.<br /><br />So I repeat my much earlier question to you...<br /><br /><I hope to put on an informal discussion of the Orbital Atmospheric Gatherer at noon, probably on Tuesday, May 22, at the ATWG conference in Dallas. /><br /><br />So? How did it go? Did the audience love it or hate it?

 

[keermalec]

OK I've been looking into the atmospheric gatherer concept and have come up with some figures. The aim here is to determine very simply if the idea is feasible at all.<br /><br />I imagine a low-orbiting vehicle equiped with a Nitrogen-propelled ion drive, powered by solar panels during the day and batteries during the night. The air is compressed using a Rotary-vane type vacuum pump. It is then liquified and separated into Oxygen and Nitrogen. Excess heat is evacuated with a radiator, and the Liquid Oxgen and Nitrogen are stored in actively coolled tanks.<br /><br />Components are therefore:<br /><br />Air liquifier (assume 6.5 kg/kg air/hour requiring 400 J/kg air)<br />LOX tank (assume 0.025 kg/kg LOX)<br />LN tank (assume 0.025 kg/kg LN)<br />Radiators (assume 10.5 kg/kg air liquified/hour)<br />Solar panels (assume 90 w/kg)<br />Batteries (assume silver-zinc batteries at 800 W/kg and 720 KJ/kg)<br />Ion thruster (assume 0.042 N/kg thrust and ISP 3940s requiring 50 W/kg)<br />Vacuum pump (assume 0.22 kg air/hr/kg)<br />structure, avionics (assume 10% of total mass)<br /><br />Air density at 150 km is around 10E-9 jg/m3.<br /><br />Orbital velocity at that altitude is 7.82 km/s<br /><br />Air drag is calculated by<br /><br />D = 0.5 * v^2 * d * dc * a / m<br /><br />D = air drag in Newtons<br />v = velocity in m/s<br />d = density in kg/m3<br />dc = vehicle air drag coefficient (2.2 for a typical satellite configuration, 1 for a more rounded body, <1 for an aerodynamic body)<br />a = vehicle air <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>